2011 GESTATIONAL DIABETES UPDATE
compiled by Kristin Effland, LM, CPM

In 2011 the International Association of Diabetes and Pregnancy Study Group Consensus Panel (IADPSGP) released Guidelines for the Diagnosis of Hyperglycemia in Pregnancy. These Guidelines differ significantly from previous obstetrical guidelines followed by many providers in the US.

For more information about what the American Diabetes Association and the International Association of Diabetes and Pregnancy Study Groups have to say about Gestational Diabetes and the hemoglobin A1c lab test, click here.

In response to the 2011 IADPSGP Guidelines, ACOG (the American College of Obstetricians and Gynecologists) released "Screening and Diagnosis of Gestational Diabetes Mellitus: ACOG Committee Opinion Number 504" published in September 2011. Vol. 118(3), pp. 751-753.

At this time, the ACOG Committee on Obstetric Practice continues to recommend the following:

All pregnant women should be screened for GDM, whether by patient history, clinical risk factors, or a 50-g, 1-hour loading test to determine blood glucose levels.

The diagnosis of GDM can be made based on the result of the 100-g, 3-hour oral glucose tolerance test, for which there is evidence that treatment improves outcome. Either the plasma or serum glucose level established by Carpenter and Coustan or the plasma level designated by the National Diabetes Data Group are appropriate to use (see Table 1). A positive diagnosis requires that two or more thresholds be met or exceeded.

Diagnosis of GDM based on the one-step screening and diagnosis test outlined in the International Association of Diabetes in Pregnancy Study Group guidelines is not recommended at this time because there is no evidence that diagnosis using these criteria leads to clinically significant improvements in maternal or newborn outcomes and it would lead to a significant increase in health care costs.

ACOG also notes that "The National Institutes of Health is planning a Consensus Development Conference to determine the optimal approach to screening and diagnosis in the United States. Consensus regarding optimal diagnostic criteria among the many groups and professional organizations will further much needed research regarding the benefits and harms of screening and diagnosis of GDM."

Best practices regarding Gestational Diabetes are being reconsidered because of the many varied perspectives on the evidence. Below is an outline of the most recent published information regarding Gestational Diabetes.

In May 2008, the US Preventative Services Task Force (USPSTF) concluded that:

The current evidence is insufficient to assess the balance of benefits and harms of screening for gestational diabetes mellitus (GDM), either before or after 24 weeks gestation.

Nearly all women should be encouraged to achieve moderate weight gain based on their BMI & to participate in physical activity.

Although screening and early treatment of GDM reduces macrosomia, and although 1 trial suggests the possibility of other health benefits, the overall evidence is poor to determine whether maternal or fetal complications are reduced by screening.

The American Academy of Family Physicians (AAFP) on Diagnosis & Management of GDM (July 2009) finds that:

“Although earlier delivery reduced the risk of macrosomia, it did not reduce rates of brachial plexus injuries, hypoglycemia, or clavicle fractures.” (61)

“A financial-based decision analysis argues against facilitated delivery; an estimated 443 elective cesarean deliveries need to be performed to prevent one case of brachial plexus injury, at a cost of $930,000 (in 1996).” (61)

“Based on the limited data, as well as the medicolegal climate, many physicians still opt to facilitate delivery before 39 weeks' gestation. If this option is chosen in the absence of maternal or fetal compromise, amniocentesis should be strongly considered to assess for fetal lung maturity.” (61)

Scrutinizing the study results reveals that the Mean Birth Weight Difference was only 3.7 ounces, and the Neonatal Fat Mass Avg. Difference was only 1.3 ounces

For comparison, consider that the percentage of LGA Babies in the CPM 2000 study 24.3% and yet the C/S rate was 3.7%!

Importantly, this and other related studies have begun to conclude that “Increased birth weight and neonatal fat mass may have long-term health implications for the offspring of mothers with gestational diabetes mellitus, including an increased risk of impaired glucose tolerance and childhood obesity.” (Landon, 1346)

An important consideration with the HAPO study is that the effects are determined by odds ratios. Odds tend to inflate the effect size of an analysis (esp. if the events being studied are relatively common). Whereas probabilities/Relative Risks are relatively easy to interpret, odds can be tricky. In fact, odds ratios can illegitimately inflate the effect size substantially.

Despite a higher rate of induction, the rates of C/S were similar (31% and 32%; RR, 0.97; CI, 0.81 to 1.16; P=0.73).

For comparison, the C/S rate in the CPM 2000 study was 3.7%.

The increased NICU admissions and increased rates of induction may both be related to the knowledge of the diagnosis by the attending physician.

“The earlier gestational age at birth as a consequence of the induction of labor may have contributed to the reduction in serious perinatal outcomes.” (2483)

Or to Iatrogenic prematurity necessitating NICU admission!!! (This is not concluded by study authors, but seems like a major oversight in my opinion)

“Long-term follow-up is needed to assess whether the lower birth weights among the infants in the intervention group will translate into reduced rates of [impaired glucose tolerance, diabetes, & GDM].” (2484)

At three months postpartum, data on the women's mood and quality of life, available for 573 women, revealed lower rates of depression and higher scores, consistent with improved health status, in the intervention group.

A study published in August 2010, found a reduced incidence of gestational diabetes with bariatric surgery:

Obese women who have weight loss surgery before they get pregnant are three times less likely to develop gestational diabetes and are also less likely to require a cesarean section.

Most of the women in the study had a gastric bypass operation, with some opting for an adjustable band procedure.

Like all operations, however, bariatric surgery is not without risk.

There were 346 women who had a delivery before bariatric surgery, and 354 had a delivery after bariatric surgery. Women with delivery after bariatric surgery had lower incidences of GDM (8% vs 27%, odds ratio (OR) 0.23, (95% CI 0.15 to 0.36) and cesarean section (28% vs 43%, OR0.53, 95% CI 0.39 to 0.72) than those with delivery before bariatric surgery.